Expansible boring tool



May 5, 1925e A. GOSPER EXFANSIBLE BORING TOOL Spe# Filed Jan. 14, 1925,..//fatented May 5, i925,

UNITED staresu PAT'ET OFFICE.

ASSIGNOR TO GEORGE HUGH FOSTER, SOUTH WALES, AUSTRALA.

EXPANSIBLE Application filed January To all 'whom it may concern:

Be it known that L AMos GrosPER, a subject ot' the King of GreatBritain, residing at Camperdown, near Sydney, in the State of New SouthWales, Commonwealth of Australia, have invented new and usefulImprovements in Expansible Boring Tools (for which ll have filedapplication 1n Australia, Dec. 11, 1923), of which thel followin is aspecification.

his invention-relates 'to an improved expansible boring tool for formingundercut holes in timber and other material, and it has been devisedhaving for its principal object the provision of a boring tool that willaccurately and expeditiously bore holes of uniform width for portion oftheir length but enlarged at their inner ends, while ,simultaneouslywith thaformation ofthe said enlarged portions counter-sinks are formedat the entrance ends of the holes. Holes so formed are used in thejointing o adjacent members in woodwork bythe use of trenails which areadapted to be expanded at their, end portions, and for various otherpurposes in joinery.

The invention provides an im roved expansible boring tool which isself-contained and furnished with means for stabilizing its operativeintegers, and means for synchronously returning the cutter and itscontrol member to initial position immediately upon completion ofboring.

Reference being had to the accompanying drawings Figure 1 is aperspective view of the improved expansible .boring tool.

Figure 2 is a vertical sectional view of the boring tool, showing thearrangement of its integers prior to boring.

Figure 3 is a vertical sect-ion showing the arrangement of the toolintegers when that portion of the hole of'uniform width is being bored.

Figure 4 is a vertical section illustrating the integers of the toolwhen the lower eX- panded end of the hole isbeing bored and the entranceend of the hole is being countersunk. ,i

The improved expansible boring tool comprises a cylindrical casing 2tted with a screw-cap 3, and having an upper ball bearing 4 and a lowerballV bearing 5 for a spindle 6 which latter is a slidable fit in a 0FMARRICKVILLE, NEAR SYDNEY, NEW

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7 at its upper end to facilitate the attachl ment of tthe boring tool toa drilling machine or the like, whereby the spindle 6 can be rotated athigh speed.

Formed in the lower end of said spindle 6 is a slotway 8, wherein isaccommodated a control tongue.9, that is pivoted at its lower end upon ashort pin 10 in said slotway. This control ton e has a straight edgeortion 11, which oes not project eX- terior y of the spindle 6 and it isconstructed having an upper end ortion 12 that inclines outwardly fromsaid straight edge portion.

A tool-holder 13 is formed on, or may be afhxed to, the lowerl end ofthe pivoted control ton ue 9, and fitted in said toolholder is a oringtool or cutter 14 havin its op osite edges concaved and. thickene at itsower en A bevelled cutting member 15 is formed on the. lower end of thesaid tool holder 13, and it serves to countersink the upper end of thehole being bored by the tool.

Fitted around the spindle 6, beneath the upper ball-bearing 4 is athrust collar 16 having fibre seating washers 17. A coiled spring 18encircles the spindle 6 and the upper end of the control tongue 9, andit is seated against the lower ball-bearing 5 and the washers 17 on thethrust collar 16.

In use, the tang 7 is first connected to a drilling machine or the like,and the spindle 6 is rotated at comparatively highs eed and moveddownwardly through the bearings 4 and 5 in the casing 2 against thetension of the coiled spring 18. The boring tool or cutter 14 is thusbrought against the work-piece and it bores a hole of predetermineddepth and having uniform width, until such time as the outwardlyprojecting and inclined portion 12 of the pivoted control tongue 9 isforced inwardly into the slotway 8 by contact with the lower ballbearing 5-see Figure 4. As the upper end of the control tongue 9 ismoved inwardly `into said s lotway 8, the tool holder 13 is movedslightly outwardly and the boring tool or cutter 14 is inclined to theaxis ot the spindle 6 to progressively form a hole portion of increasingwidth at the lower end of 'the hole portion which is ofI uniformallwidth. Simultaneously with the outward' atI the lower end of the toolholder v13 bears.

against the work-piece and counter-sinks the. ent-rance end of the holehaving its' major portion of uniform width.

The tension exerted upon the coiled spring 18 encircling the'spindle 6during the feeding movement of said spindle ensures the synchronousreturn of the cutter 14 andthe pivoted control tongue 9 to initialposition immediately following the boring of a hole of the characterdescribed.

The lower end of the cylindrical casing is, or mav be, provided havingspikes 19 to grip t e work-piece,,and said easing may also be formedhaving milled portions 20 to enable a tight rip to be maintained uponthe tool during oring operations.

It will be readily understood by artisans that dii'erent cutters 14 canbe interchangeably fitted in the tool-holder 13 and that requiredadjustments can be made in the integers of the improved expansibleboring tool whereby holes of different length and having varying degreesof undercut at their lower ends can be rapidly formed.

What I do claim is 1. An expansible boring tool comprising, a casing, anupper and a lower ball-bearing in said casing, a spindle longitudinallymovable in said ball-bearings, a slotway formedin said spindle, a tonguepivoted at its lower end in said slotway, an outwardly `said tongueheilig adapted to contact with the lower ball-bearing when a hole ofuniform width of required depth has been bored`and thus cle-align saidcutting tool to undercut the hole and complete the boring operation. i

2. An expansible boring tool according to claim 1, wherein thetool-holder is Constructed having a bevelled cutting member to formcounter-sinks at. the entrance ends of the holes being boredsimultaneously with the undercutting of said holes at the inner ends.

In testimony whereof I affix my signature in'presence of two witnesses.

AMOS GOSPER. Witnesses:

M. STARFIELD,

W. J. CREAGH.

